scholarly journals Division of labor increases with colony size, regardless of group composition, in the social spiderStegodyphus dumicola

2019 ◽  
Author(s):  
Colin M. Wright ◽  
James L. L. Lichtenstein ◽  
C. Tate Holbrook ◽  
Justin Pretorius ◽  
Noa Pinter-Wollman ◽  
...  
Keyword(s):  
Division Of Labor ◽  
Group Size ◽  
Colony Size ◽  
Prey Capture ◽  
Work Organization ◽  
Group Function ◽  
Social Spiders ◽  
Eusocial Insects ◽  
Save Energy ◽  
Web Construction

AbstractDivision of labor (DOL) is a pattern of work organization where individual group members specialize on different tasks. DOL is argued to have been instrumental for the success of eusocial insects, where it scales positively with group size both within and across species. Here we evaluate whether DOL scales positively with group size in a society of cooperative breeders (social spiders) and whether this pattern is impacted by the behavioral composition of the group. To do this we engineered experimental colonies of contrasting group sizes and behavioral compositions and tracked individuals participation in two colony maintenance tasks: prey capture and web construction. As with some eusocial insects, we found that larger groups exhibited DOL metrics up to 10-times greater than smaller groups, conveying that individuals specialize on particular tasks more in larger colonies. This scalar relationship did not differ by a groups behavioral composition, though groups composed of only bold spiders exhibited reduced DOL relative to all-shy or mixed groups. We also found that per capita participation in prey capture, but not web construction, decreased as a function of group size. This suggests that individuals in larger groups may save energy by reducing their involvement in some tasks. Together, our results convey that similar scalar relationships between DOL and group size can emerge both inside and outside the eusocial insects. Thus, theory developed for understanding DOL in eusocial societies may inform our understanding of group function in a larger swath of animal social diversity than is broadly appreciated.SignificanceStatementDivision of labor (DOL) has been a major area of research in the eusocial insects for decades, and is argues to underlie their ecological success. Only recently have other social arthropods, such as social spiders, been considered for studies concerning DOL. Given their smaller colony sizes, and absence of morphological castes, DOL was not thought to be an important facet of spider societies. However, we found that spider societies do indeed exhibit high degrees of DOL that is positively correlated to colony size, as seen in many eusocial insects. These findings suggest that the scalar relationship between group size and social organization seen in social insects is likely generalizable to a larger diversity of social taxa, and that cooperative breeders can show levels of division of labor equaling or exceeding those of eusocial systems evaluated to date.

scholarly journals Morphological and genomic shifts in mole-rat ‘queens’ increase fecundity but reduce skeletal integrity

2020 ◽  
Author(s):  
Rachel A. Johnston ◽  
Philippe Vullioud ◽  
Jack Thorley ◽  
Henry Kirveslahti ◽  
Leyao Shen ◽  
...  
Keyword(s):  
Division Of Labor ◽  
Morphological Plasticity ◽  
Skeletal Morphology ◽  
Eusocial Insects ◽  
Mole Rat ◽  
Gene Regulatory ◽  
Reproductive Division Of Labor ◽  
Reproductive Division ◽  
Skeletal Integrity ◽  
Vertebral Growth

AbstractIn some mammals and many social insects, highly cooperative societies are characterized by reproductive division of labor, in which breeders and nonbreeders become behaviorally and morphologically distinct. While differences in behavior and growth between breeders and nonbreeders have been extensively described, little is known of their molecular underpinnings. Here, we investigate the consequences of breeding for skeletal morphology and gene regulation in highly cooperative Damaraland mole-rats. By experimentally assigning breeding ‘queen’ status versus nonbreeder status to age-matched littermates, we confirm that queens experience vertebral growth that likely confers advantages to fecundity. However, they also up-regulate bone resorption pathways and show reductions in femoral mass, which predicts increased vulnerability to fracture. Together, our results show that, as in eusocial insects, reproductive division of labor in mole-rats leads to gene regulatory rewiring and extensive morphological plasticity. However, in mole-rats, concentrated reproduction is also accompanied by costs to bone strength.

scholarly journals Morphological and genomic shifts in mole-rat 'queens' increase fecundity but reduce skeletal integrity

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Rachel A Johnston ◽  
Philippe Vullioud ◽  
Jack Thorley ◽  
Henry Kirveslahti ◽  
Leyao Shen ◽  
...  
Keyword(s):  
Division Of Labor ◽  
Morphological Plasticity ◽  
Skeletal Morphology ◽  
Eusocial Insects ◽  
Mole Rat ◽  
Gene Regulatory ◽  
Reproductive Division Of Labor ◽  
Reproductive Division ◽  
Skeletal Integrity ◽  
Vertebral Growth

In some mammals and many social insects, highly cooperative societies are characterized by reproductive division of labor, in which breeders and nonbreeders become behaviorally and morphologically distinct. While differences in behavior and growth between breeders and nonbreeders have been extensively described, little is known of their molecular underpinnings. Here, we investigate the consequences of breeding for skeletal morphology and gene regulation in highly cooperative Damaraland mole-rats. By experimentally assigning breeding 'queen' status versus nonbreeder status to age-matched littermates, we confirm that queens experience vertebral growth that likely confers advantages to fecundity. However, they also up-regulate bone resorption pathways and show reductions in femoral mass, which predicts increased vulnerability to fracture. Together, our results show that, as in eusocial insects, reproductive division of labor in mole-rats leads to gene regulatory rewiring and extensive morphological plasticity. However, in mole-rats, concentrated reproduction is also accompanied by costs to bone strength.

scholarly journals Properties of orb weaving spider glycoprotein glue change during Argiope trifasciata web construction

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Brent D. Opell ◽  
Sarah D. Stellwagen
Keyword(s):  
Young’S Modulus ◽  
Material Properties ◽  
Prey Capture ◽  
Young's Modulus ◽  
Progressive Increase ◽  
New Materials ◽  
Web Documents ◽  
Aqueous Layer ◽  
Argiope Trifasciata ◽  
Web Construction

AbstractAn orb web’s prey capture thread relies on its glue droplets to retain insects until a spider can subdue them. Each droplet’s viscoelastic glycoprotein adhesive core extends to dissipate the forces of prey struggle as it transfers force to stiffer, support line flagelliform fibers. In large orb webs, switchback capture thread turns are placed at the bottom of the web before a continuous capture spiral progresses from the web’s periphery to its interior. To determine if the properties of capture thread droplets change during web spinning, we characterized droplet and glycoprotein volumes and material properties from the bottom, top, middle, and inner regions of webs. Both droplet and glycoprotein volume decreased during web construction, but there was a progressive increase in the glycoprotein’s Young’s modulus and toughness. Increases in the percentage of droplet aqueous material indicated that these increases in material properties are not due to reduced glycoprotein viscosity resulting from lower droplet hygroscopicity. Instead, they may result from changes in aqueous layer compounds that condition the glycoprotein. A 6-fold difference in glycoprotein toughness and a 70-fold difference in Young’s modulus across a web documents the phenotypic plasticity of this natural adhesive and its potential to inspire new materials.

Eusocial Insects as a Model for Understanding Altruism, Cooperation, and Levels of Selection

2020 ◽  
Author(s):  
Heikki Helanterä
Keyword(s):  
Natural Selection ◽  
Division Of Labor ◽  
Social Insect ◽  
Social Evolution ◽  
Inclusive Fitness ◽  
Family Structures ◽  
Major Transitions ◽  
Eusocial Insects ◽  
Insect Societies ◽  
Evolutionary Success

If the logic of natural selection is applied strictly at the level of individual production of offspring, sterile workers in insect societies are enigmatic. How can natural selection ever produce individuals that refrain from reproduction, and how are traits of such individuals that never produce offspring scrutinized and changed through natural selection? The solution to both questions is found in the family structures of insect societies. That is, the sterile helper individuals are evolutionary altruists that give up their own reproduction and instead are helping their kin reproduce and proliferate shared genes in the offspring of the fertile queen. Selection in such cases is not just a matter of individual’s direct reproduction, and instead of own offspring, the currency of the evolutionary success of sterile individuals is inclusive fitness. The concept of inclusive fitness and the process of kin selection are key to understanding the magnificent cooperation we see in insect societies, and reciprocally, insect societies are key case studies of inclusive fitness logic. In extreme cases, such as the highly advanced and sophisticated societies of ants, honeybees, and termites, the division of labor and interdependence of colony members is so complete, that it is justified to talk about a new level of evolutionary individuality. Such increases in the hierarchical complexity of life are called major transitions in evolution. We see adaptations of the colony, rather than individuals, in, e.g., their communication and group behaviors. The division of labor between morphologically differentiated queens and workers is analogous to germline-soma separation of a multicellular organism, justifying the term superorganism for the extreme cases of social lifestyle. Alongside these extreme cases, there is enormous diversity in the social lifestyles across social insect taxa, which provides a window into the balance of cooperation and conflict, and individual reproduction and helping others, in social evolution. Over the last decades, social insect research has been an area where the theoretical and empirical understanding have been developed hand in hand, together with examples of wonderful natural history, and has tremendously improved our understanding of evolution.

scholarly journals Resting networks and personality predict attack speed in social spiders

2019 ◽  
Author(s):  
Edmund R. Hunt ◽  
Brian Mi ◽  
Rediet Geremew ◽  
Camila Fernandez ◽  
Brandyn M. Wong ◽  
...  
Keyword(s):  
Social Network ◽  
Developmental Stages ◽  
Prey Capture ◽  
Large Prey ◽  
Interaction Patterns ◽  
Social Spiders ◽  
Behavioral Traits ◽  
The Social ◽  
Group Members ◽  
Behavioral Attributes

AbstractGroups of social predators capture large prey items collectively, and their social interaction patterns may impact how quickly they can respond to time-sensitive predation opportunities. We investigated whether various organizational levels of resting interactions (individual, sub-group, group), observed at different intervals leading up to a collective prey attack, impacted the predation speed of colonies of the social spider Stegodyphus dumicola. We found that in adult spiders overall group connectivity (average degree) increased group attack speed. However, this effect was detected only immediately before the predation event; connectivity two and four days before prey capture had little impact on the collective dynamics. Significantly, lower social proximity of the group’s boldest individual to other group members (closeness centrality) immediately prior and two days before prey capture was associated with faster attack speeds. These results suggest that for adult spiders, the long-lasting effects of the boldest individual on the group’s attack dynamics are mediated by its role in the social network, and not only by its boldness. This suggests that behavioural traits and social network relationships should be considered together when defining keystone individuals in some contexts. By contrast, for subadult spiders, while the group maximum boldness was negatively correlated with latency to attack, no significant resting network predictors of latency to attack were found. Thus, separate behavioural mechanisms might play distinctive roles in determining collective outcomes at different developmental stages, timescales, and levels of social organization.Significance statementCertain animals in a group, such as leaders, may have a more important role than other group members in determining their collective behavior. Often these individuals are defined by their behavioral attributes, for example, being bolder than others. We show that in social spiders both the behavioral traits of the influential individual, and its interactions with other group members, shape its role in affecting how quickly the group collectively attacks prey.

scholarly journals Fluctuating survival selection explains variation in avian group size

2016 ◽  
Vol 113 (18) ◽  
pp. 5113-5118 ◽  
Author(s):  
Charles R. Brown ◽  
Mary Bomberger Brown ◽  
Erin A. Roche ◽  
Valerie A. O’Brien ◽  
Catherine E. Page
Keyword(s):  
Group Size ◽  
Colony Size ◽  
Information Transfer ◽  
Size Variation ◽  
Directional Selection ◽  
Net Benefit ◽  
First Case ◽  
Survival Selection ◽  
Wide Range ◽  
Directional Change

Most animal groups vary extensively in size. Because individuals in certain sizes of groups often have higher apparent fitness than those in other groups, why wide group size variation persists in most populations remains unexplained. We used a 30-y mark–recapture study of colonially breeding cliff swallows (Petrochelidon pyrrhonota) to show that the survival advantages of different colony sizes fluctuated among years. Colony size was under both stabilizing and directional selection in different years, and reversals in the sign of directional selection regularly occurred. Directional selection was predicted in part by drought conditions: birds in larger colonies tended to be favored in cooler and wetter years, and birds in smaller colonies in hotter and drier years. Oscillating selection on colony size likely reflected annual differences in food availability and the consequent importance of information transfer, and/or the level of ectoparasitism, with the net benefit of sociality varying under these different conditions. Averaged across years, there was no net directional change in selection on colony size. The wide range in cliff swallow group size is probably maintained by fluctuating survival selection and represents the first case, to our knowledge, in which fitness advantages of different group sizes regularly oscillate over time in a natural vertebrate population.

scholarly journals Producers and scroungers: feeding-type composition changes with group size in a socially foraging spider

2016 ◽  
Vol 283 (1828) ◽  
pp. 20160114 ◽  
Author(s):  
Marlis Dumke ◽  
Marie E. Herberstein ◽  
Jutta M. Schneider
Keyword(s):  
Group Size ◽  
Size Effects ◽  
Feeding Behaviour ◽  
Prey Capture ◽  
Cost Benefit ◽  
Theoretical Models ◽  
Food Sources ◽  
Feeding Types ◽  
Trade Offs ◽  
Feeding Type

In groups of socially foraging animals, feeding behaviour may change with group size in response to varying cost–benefit trade-offs. Numerous studies have described group-size effects on group-average feeding behaviour, particularly emphasizing an increase in scrounging incidence for larger groups, where individuals (scroungers) feed from the food sources others (producers) discovered. However, individual variation in feeding behaviour remains unconsidered in the vast majority of these studies even though theoretical models predict individuals to specialize in feeding tactic and anticipate higher scrounger-type frequencies in larger groups. We combined group-level and individual-level analyses of group-size effects on social foraging in the subsocial spider Australomisidia ergandros . Lending novel experimental support to model predictions, we found that individuals specialize in feeding tactic and that higher scrounging and lower producing incidence in larger groups were mediated through shifts in the ratio of feeding types. Further, feeding-type specialization was not explained by innate individual differences in hunting ability as all feeding types were equally efficient in prey capture when foraging alone. Context adaptivity of feeding behaviour might allow this subsocial species to succeed under varying socioecological conditions.

scholarly journals Mutational meltdown of microbial altruists in Streptomyces coelicolor colonies

2020 ◽  
Author(s):  
Zheren Zhang ◽  
Bart Claushuis ◽  
Dennis Claessen ◽  
Daniel E. Rozen
Keyword(s):  
Division Of Labor ◽  
Streptomyces Coelicolor ◽  
Fold Increase ◽  
Base Substitution ◽  
Natural Mode ◽  
Genomic Deletions ◽  
Eusocial Insects ◽  
Individual Fitness ◽  
Mutant Cells ◽  
Mutational Meltdown

AbstractIn colonies of the filamentous multicellular bacterium Streptomyces coelicolor, a sub-population of cells arise that hyper-produce metabolically costly antibiotics, resulting in a division of labor that maximizes colony fitness. Because these cells contain large genomic deletions that cause massive reductions to individual fitness, their behavior is altruistic, much like worker castes in eusocial insects. To understand the reproductive and genomic fate of these mutant cells after their emergence, we use experimental evolution by serially transferring populations via spore-to-spore transfer for 25 cycles, reflective of the natural mode of bottlenecked transmission for these spore-forming bacteria. We show that, in contrast to wild-type cells, altruistic mutant cells continue to significantly decline in fitness during transfer while they delete larger and larger fragments from their chromosome ends. In addition, altruistic mutants acquire a roughly 10-fold increase in their base-substitution rates due to mutations in genes for DNA replication and repair. Ecological damage, caused by reduced sporulation, coupled with irreversible DNA damage due to point mutation and deletions, leads to an inevitable and irreversible type of mutational meltdown in these cells. Taken together, these results suggest that the altruistic cells arising in this division of labor are equivalent to reproductively sterile castes of social insects.

scholarly journals Work Organization and Professionalization in New Media Industry – The Case of a Finnish Company

2012 ◽  
Vol 2 (1) ◽  
pp. 23 ◽  
Author(s):  
Arja Haapakorpi
Keyword(s):  
Project Management ◽  
New Media ◽  
Division Of Labor ◽  
Turning Point ◽  
Work Organization ◽  
Creative Work ◽  
Media Industry ◽  
New Business ◽  
Professional Employees ◽  
Media Company

The article explores work organization in one new media company in a turning point of the business, in the 2000s. The company had changed from a small workshop to a medium-sized company in a few years. Growth, increasing competition, and uncertainty of profitability had altered the management and work organization. An approach of governance, aimed at efficiency and economy, was systematically implemented; the working methods were standardized, strict division of labor was carried out, and the professional qualifications were mainstreamed according to the business. The professional employees appreciated the new business-like management, but discovered that their opportunities for creative work were diminished with decreasing resources and a new project management pattern.

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